Water weight can fluctuate so much that I wonder if that’s your cause. If you aren’t hungry, don’t eat. Eventually your hunger will catch up. I promise you. Don’t eat when you aren’t hungry. Refuel with healthy things.
Everybody’s metabolism is different. Some people get the runs, as usual I suffer from constipation. Although your “gained on to little, lost when more” sounds more like you are misreading the way your water weight is coming back.
If you really want to bump up your caloric intake stop drinking water and start drinking milk. Half a gallon would be an additional 1,200 calories on top of your solid food calories.